I’m just wondering which is the most correct way to write the name of this piping ornamentation, and from where it comes from…
crann seems to mean “tree”
I suspect that the Irish cran and the Scottish crunluath (The later has about six different spellings) are probably related. The fingering is kind of similar. On the GHB you play gracenotes with your r1, l3, and l2, sequentially. Kind of a cran backwards. The right hand pinky finger does things too, in most, but not all, cases.
This should help you to remember the spelling. Not sure if it improves your crans, though!
It’s creathaghmhaidhionn. TWO Ns. 
Strewth, Nano, that’s worse than engineering the elements of the thing itself!
I’d always assumed (on the basis of no serious evidence) that “cran” was correct (in English!) - certainly it was the way I first encountered it spelled on record sleeve bumf etc. - and that the two nn version was an affectation, ye oldey worldey bogge-oirishey factor at work; though of course once adopted into English, normal English spelling rules apply, so the n doubles in e.g. “cranning” ('cos the i would otherwise make the a “say its name”).
Breadan Breathnach’s notes in Irish on ornaments in Ceol Rince1 have “crannail”… which proves nothing about how it is/should be written in English. Desi Wilkinson’s band Cran have only one n…
Websearching on either spelling fails to bring up anything to do with piping or music at all on the first page of hits (I don’t go any further). Wiktionary has the Irish/Gaelic word “crann” but, as noted above, it doesn’t seem to have a relevant meaning. Searching on “cran piping” gets the town, the band and (!!!) some mentions of the musical term at last. Going beyond the first page there are plenty of one-n uses from what appear to be serious piping sources, though a quick glance at one has both spellings in it!!! The equivalent two-n search (1st pages only again) gets nothing much musical - back to the Crann Tara etc.
Inconclusive, then… pick your own!
Oh, crap. Now I’ll have to spell it “crannnning”.
In my Irish dictionary there is no entry for cran, but there is a lengthy one for crann:
crann, m, (gs & npl -ainn, gpl ~, pl -a used in certain phrases)
- tree
- mast
- stock, handle
- shaft, beam
- wooden implement, stick
- wooden structure, vessel, or frame (interesting that crann ceoil means woodwind instrument)
- penis
- stick used in casting lots crannchur lottery
- fig. teacht i gcrann to grow in maturity (many other phrases are given)
- wooden saor crainn carpenter.
There then follows a host of words relating to trees, forests, wooden things, etc. beginning with crann or similar. Nothing remotely relating to the musical movement.
Now what about Scottish Gaelic? Once again no cran, but
crann n m a tree, wooden nail or spike, a plough, a mast, a barrell, a lot or ballot, an arrow, a coffin, drone of a pipe
Followed by many words beginning in crann relating to trees and wooden things.
Things become more clear when we move to crun.
crun a crown, n m a five-shilling piece, crown of the head
crunluath n m a quick measure in Highland music, final measure of a pibroch, a seal. Also crunnluath.
In fact, in piobaireachd, a crunluath is a specific ornament, a rapid bubbling of gracenotes. The final variation or variations of a piobaireachd might feature this movement and are thus called by that name.
In The Highland Bagpipe and its Music Roderick Cannon says:
(In discussing piobaireachd variations) “Finally comes the “Crunluath” or more properly Crunluth. Again, the true meaning of the word is not known but “crowning movement” is not a bad description… Next and last comes Crunluath mach. “Mach” or “a mach” means “out” but it is not easy to guess the true meaning of the phrase here. The “mach” is a real fireworks display: it sounds much faster than the plain Crunluath doubling, although the actual tempo is not much different.”
He then goes on to discuss further variations including Crunluath Fosgailte and Crunluath Breabach.
By the way “luath” means fast so “crunluath” seems to mean the “quick crowning”.
So to go back to the original question, I suppose in English it’s “cran” which isn’t an Irish word, “crann” for a tree etc. The original Gaelic musical term seems to be “crun”.
Then crann the lot of you. I can’t do 'em anyway.
I don’t think that’s necessarily true. The modern Scottish piping word “Crunluath” seems to originate with Angus Mackay. Donald MacDonald, the publisher of the first piobaireachd book in staff notation, around 1820, and a Gaelic speaker, wrote “Creanluidh.” In Gesto (also about 1820, iirc) it’s “Crouluigh”. Joesph Macdonald, the first person to write about highland piping, in 1760, did not use any word for the ornament but had a compound name (although by the time his book was published in the 1800’s, someone saw a need to add it in).
All this time, I thought it was “cram,” as in “cram the whistle in your mouth and blow.” 
I did the same researches Jem did before opening the thread, but couldn’t find anything decisive.
But i did notice that Nano insisted on the double n version on a couple of other posts. What is your source?
And i can’t see the relation between crown and music (but maybe there’s an english meaning I don’t know…).
Did I insist? If so, I guess I don’t really insist so much these days, now, so scratch that…I guess I’ve mellowed or something. But my preference continues to be to spell it that way, for myself.
I couldn’t begin to tell you for sure because it all goes back a ways, but I’m pretty sure the first time I came across the term at all was in the Timber flute tutor book by Fintan Vallely. Memory tells me that the double N was the spelling; it’s the sort of thing that would strike me. I’ve seen it elsewhere enough, too (unfortunately I’ve forgotten where that would be, now), and in the past I assumed that the single N spelling must have been a mistake, mainly because 1) I’ve found no single-N version in Irish dictionaries, and 2) the fact that in your usual dictionaries the double-N version has no musical references never bothered me; after all, some usages can be so obscure or occupation-specific as to never make it into the definition selections of standard dictionaries. And I think no one would deny that a “crann” (or “cran”) in the piperly sense is pretty darned obscure, just like the noun “scrape” as relates to uilleann pipe reedmaking; you won’t find that in Merriam Webster. But, so much for that reasoning. 
In any case, in the sources I had earlier read and was learning from the double-N version seemed to tend to predominate - this may be purely by chance - and thus my preference was colored.
The “crunluath” is the “quick crowning”, the flashy finale of the piobaireachd.
That’s great! Because in the Gaelic dictionary there is:
creanaich v tremble, shiver
which is the exact way these ornaments were often called in English, “shakes”.
Interesting stuff on the possible Irish/Gaelic etymology - the “shake” thing (in English also an archaic term for a trill) looks like the right derivation - and both forms given above have the single n.
Nano, I’ve just checked my old copy of Fintan Vallely’s Timber tutor and he has “cran” with one n - though the title of the section is “Cranning” !!! (See above!). Also, the translation (the author’s own!) of Breathnach’s aforementioned text on Terry McGee’s website has one n in the (English) root word. Do we need better authority?
Ooo – neat.
I double checked Joseph MacDonald. He spells creanludh. He refers to all ornaments as “shakes” interchangeably. But what he calls a creanludh is what we would call an edre. a-e-a-f-a-E (i.e. L3 and L2 blipped over a closed chanter (R1,2, and 3 all down) but always ending on a short L3.
What we call a crunluath, he refers to as “torludh + creanludh”
In one Gaelic-English dictionary, crean is given as a word for smart. I assume that means to move smartly, rather than intellegence. MacDonald also gives a shake called a barludh. curiously, the English “bar” is given the translation of crann. But Gaelic bar has several translations, including a dart.
Tor, interestingly, translates as tower – There’s not much in the way it’s played or the way it sounds that reminds me of a tower, but the grip portion kind of looks like a tower when written in musical notation – especially if you put the beams on the bottom instead of the top.
Well, I’ll be. I gave mine away some time back so I can’t compare. Are you sure it’s not a revised edition and Vallely’s not just confused?
Yes. Yes, dammit, I DO.
Well, my copy was bought back in the 1980s and is the edition with the garish lemon and orange cover - not sure if it’s the original version, but it certainly isn’t the more recent revised one.
Ha! Ball’s in your court. (Match point for 70-68 in the final set! But I don’t think the Yank will win this one…)
I’ll just sit here with my arms crossed and a dour look.